The present application relates to engine aftertreatment systems, and more particularly, but not exclusively, relates to an aftertreatment system for an auxiliary power unit engine carried on a vehicle.
In certain applications, a vehicle engine idles for extended periods of time to provide electrical power to accessories. This operation can generate significant amounts of unnecessary emissions because the idling engine is sized to provide propulsive power for the vehicle, which is much greater than that needed to power the accessories. To address this drawback, some vehicles include a secondary engine in a genset dedicated to powering the accessories. Typically, this secondary engine can be smaller than the engine used to propel the vehicle, and correspondingly has lower exhaust emissions that have not been subject to aftertreatment. However, even a smaller engine benefits from having aftertreatment to reduce exhaust emissions, as the untreated exhaust of a smaller engine can exceed desired emissions levels. Unfortunately, for typical applications, an aftertreatment system dedicated to the secondary engine can be cost prohibitive and/or the aftertreatment system dedicated to the secondary engine can be cost prohibitive and/or the engine cannot practically provide the conditions needed to periodically regenerate typical aftertreatment systems. Accordingly, there is a demand for further contributions in this area of technology.